What is the MCP Inspector and why do you need it during development?

When building MCP servers, you need a way to test your functionality without connecting to a full application. The Python MCP SDK includes a browser-based inspector that lets you debug and test your server in real time. Instead of writing separate test scripts or wiring up a complete client, you point the Inspector at your server file, and it gives you a graphical interface where you can list tools, list resources, list prompts, fill in arguments, and execute calls. This makes early development much faster, because you can verify each piece in isolation before integrating it into a larger application.